1. Field of the Invention
The present invention relates to a solid-state imaging apparatus including a plurality of photoelectric conversion elements configured to convert incident light to electric signals.
2. Description of the Related Art
Conventionally, a pixel circuit described in FIG. 4 of Japanese Patent Application Laid-Open No. 2009-33316 is known as a pixel circuit of a MOS solid-state imaging apparatus. Japanese Patent Application Laid-Open No. 2009-33316 discloses a configuration including a unit, in which pixels are arranged two-dimensionally, and floating diffusions (hereinafter, also called “FD”) of adjacent pixels in the vertical direction are connected electrically through connection switches.
In the configuration as shown in FIG. 4 of Japanese Patent Application Laid-Open No. 2009-33316, a condition for turning on an FD connecting transistor configured to connect the FDs of adjacent pixels is (gate high voltage of FD connecting transistor)−(reset voltage of FD)>(threshold of FD connecting transistor). If the threshold of the FD connecting transistor is high, the FD connecting transistor does not turn on, and voltages of the FDs cannot be averaged. Therefore, reset voltages of the FDs vary in the connected FDs, and a correct reference voltage (dark level) cannot be read. This affects subtraction between a light signal voltage and a reference voltage.
An object of an embodiment of the present invention is to surely turn on an FD connecting transistor in a solid-state imaging apparatus including the FD connecting transistor when turning on the FD connecting transistor.